1. Field of the Invention
This invention relates to a monitor/detector assembly through which x-ray beams in a synchrotron are transmitted and which is used to either monitor the photon beam position or detect the beam flux for such beams, and more particularly, to a new and improved monitor/detector assembly to monitor the position of the photon beams or to detect the amount of beam flux within the x-ray beams produced in the synchrotron, the monitor/detector assembly having sensors made of low atomic number material, such as aluminum or beryllium mounted on a chemical vapor deposition diamond or cubic boron nitrate foil that also can be a barrier window.
2. Background of the Invention
High energy synchrotron radiation sources are used for research in the fields of endeavor such as the fields of material science, chemistry, physics, medical and biological imaging and geophysics. In a seven (7) GeV Advanced Photon Source (APS), high brilliance and intense synchrotron radiation is generated from insertion devices (IDs). These insertion devices include different types of magnetic wigglers and undulators. It is necessary to monitor the position of the beam so that if it is being missteered, appropriate adjustments can be made. Similarly, the amount of flux within the beam may need to be detected. In certain instances, the front end or ring side of the radiation beam developed by the APS has to be separated from the downstream or working end of the beam. This separation is accomplished through a barrier window that allows the beam to be transmitted through it while at the same time forms a vacuum barrier to separate the ring side of the beam that may be maintained at a superior vacuum level of 10.sup.-10 Torr from the downstream segment of the beam that may be maintained at a lower quality vacuum level of 10.sup.-8 to 10.sup.-6 Torr.
The cross-section of beams being produced in the APS can be visualized as having a core and a surrounding halo. The hard x-ray core of the beam is of a higher energy level than the surrounding halo and therefore can cause extremely high heat loads when it impinges on certain surfaces. On the other hand, the surrounding halo portion of the beam is of a lesser energy level and does not affect as much the surfaces on which it impinges.
In a previously designed arrangement, a photon beam position monitor (PBPM) was used to determine the position of the beam within the synchrotron. The PBPM included a plurality of spaced apart blades, each of which was formed of a chemical vapor deposition (CVD) diamond core coated with a photon sensitive metal, such as tungsten, molybdenum, titanium or a titanium alloy on the order of 1-5 microns thick. Each pair of such spaced apart blades projected in opposite directions towards each other into the path of the beams and based on the amount of energy impinging on the blades, the position of the beam could be determined.
While the positioning of the beam in the APS can be determined by such PBPM's, it would be advantageous to have a monitor/detector assembly that can be readily positioned in the path of the beam without significantly affecting the beams being transmitted through the assembly. Moreover, it would be advantageous to be able to combine in a single unit the functions performed by a barrier window that is used to isolate the front end of the beamline from the downstream end of the beamline and the PBPM. By having a single unit, only one such device needs to be mounted in the path of the beam and the costs associated with producing the devices and mounting them in the synchrotron are minimized. However, the combining of such devices into a single unit cannot be at the expense of the accuracy of the PBPM because it is important to the proper operation and use of the APS to monitor the exact position of the beam so that adjustments can be made if the beam is being missteered.
Accordingly, it is an object of the present invention to provide a new and improved monitor/detector assembly for a synchrotron for monitoring the position of the photon beam or for detecting the amount of flux in the beam.
It is an object of the present invention to provide a new and improved monitor/detector assembly for a synchrotron that functions as a barrier window between the front end and downstream segment of a beamline in the synchrotron as well as enables the monitoring of the position of the photon beam or the detection of the amount of flux in the beam.
It is another object of the present invention to provide a new and improved monitor/detector assembly for a synchrotron that provides the combined functions of a window that serves as a vacuum barrier between the front end or ring side of the beamline and the downstream segment of the beamline in the synchrotron and either a photon beam position monitor that can accurately determine the relative position of the beam within the synchrotron or a beam flux detector that can evaluate the amount of flux within the beam.
It is further object of the present invention to provide a new and improved monitor/detector assembly for use in a synchrotron that combines the functions of a barrier window with a photon beam position monitor or a beam flux detector with the window being formed of a chemical vapor deposition diamond or cubic boron nitrate foil that is fused to a base flange and the position monitor or beam flux detector including sensors of low atomic number material, such as aluminum or beryllium, that are disposed on the window foil.
A still further object of the present invention is to provide a new and improved monitor/detector assembly for use in a synchrotron that combines a barrier window with a photon beam position monitor or beam flux detector with sensors of low atomic number material, such as aluminum or beryllium, being sandwiched in between the window formed of a chemical vapor deposition diamond or cubic boron nitrate foil and a front foil of similar material.